Behavior of Platinum Group during Their Pyrometallurgical Recovery from Spent Automotive Catalysts

Abstract

The behavior of platinum group metals (PGMs) during their recovery with smelting of spent automotive ceramic catalysts powder in the presence of metallic copper at elevated temperatures is studied in this paper. Two different metal recovery mechanisms proved to be active in this process: 1) Wetting of micro-dispersed particulates of PGMs in the slag by molten copper, formation of copper droplets with attracted microparticles of PGMs and settling of the molten droplets of Cu-PGMs alloy through the slag at the bottom of the crucible (“wetting”); 2) Settling of solid PGMs microparticles through the molten slag and formation of a solid solution with the molten copper at the bottom of the crucible (“settling”). The PGMs are divided in two separate groups. Platinum has under the same experimental conditions substantially higher recovery in comparison with the palladium and rhodium that behave as a group having almost identical recoveries. The heavier Pt is recovered primarily in big extent (almost 88%) through the “settling” mechanism while Pd and Rh are recovered following a more balanced mixture of both mechanisms with the “settling” one to be again more important (66% for Pd and 57% for Rh). Slag viscosity is the most important physical property and the design of an appropriate slag system is the most important issue in developing an efficient process for the recovery of PGMs.